This definition, which has not been updated since 1929, is narrower than the one used by many police departments around the country, and women's rights advocates say it leads to the under-counting of thousands of sexual assaults each year.

At a meeting in Albuquerque, N.M. on Tuesday, the FBI's Criminal Justice Advisory Policy Board voted to change the definition of rape in its Uniform Crime Reporting (UCR) Summary Reporting System, following the recommendation of a lower panel in October. The new terminology says rape is "penetration, no matter how slight, of the vagina or anus with any body part or object, or oral penetration by a sex organ of another person, without the consent of the victim."

This new definition expands the old one by taking out the requirement of a "forcible" assault and the restriction that the attack must be toward a woman. It also now includes non-vaginal/penile rape and rape by a blood relative.

"Although long overdue, we are pleased that the FBI has vetted this change extensively with its local and national law enforcement advisors and a clear consensus has emerged that a more accurate definition will better inform the public about the prevalence of serious sex crimes and will ultimately drive more resources to apprehend sex offenders," Carol E. Tracy, executive director of the Pennsylvania-based Women's Law Project (WLP), said in a statement. WLP began the campaign to redefine rape in the UCR a decade ago.

The Feminist Majority Foundation also recently led a "Rape is Rape" campaign, calling on the public to pressure the FBI to update its definition. More than 160,000 emails were sent to the FBI in support.

"It's a great victory," said Eleanor Smeal, president of Feminist Majority Foundation, in a statement. "This new definition will mean that, at long last, we will begin to see the full scope of this horrific violence, and that understanding will carry through to increased attention and resources for prevention and action."

Although Tuesday's vote was "a very big deal," according to Tracy, the official definition is not yet changed. The recommendation -- along with all the others agreed upon by the policy board at its meeting -- now goes to FBI Director Robert Mueller for final sign-off, most likely in the new year.

The FBI's current narrow definition of rape has created complications for law enforcement agencies, which can't report all of the rapes they prosecute for inclusion in federal statistics if their state or locality has a broader definition.

For example, in 2010, the Chicago Police Department reported nearly 1,400 sexual assaults. None of them, however, appeared in the federal crime report because they didn't fit the federal government's definition of rape.

"We prosecute by one criteria, but we report by another criteria," Steve Anderson, chief of the Metropolitan Nashville Police Department, told The New York Times. "The only people who have a true picture of what's going on are the people in the sex-crimes unit."

According to the federal 2010 Uniform Crime Report, there were 84,767 sexual assaults reported in 2010, a 5 percent drop from the previous year.

In a recent survey by the Police Executive Research Forum, nearly 80 percent of the 306 police departments that participated said the federal definition of rape was outdated.

On Monday, Rep. Lucille Roybal-Allard (D-Calif.) wrote an op-ed in The Hill stating that changing the FBI's definition could critically affect her work on the House Appropriations Committee.

"In the coming months, we face a tough fight to preserve funding for critical programs that aid victims and help put their assailants behind bars," wrote Roybal-Allard. "The UCR data plays a key role in the allocation of vital resources for prevention, treatment and enforcement. With so much hanging in the balance, it is imperative that the FBI move swiftly to adopt the proposed changes. By taking this simple step and updating the Bureau's definition to include all types of rape, we can make a real difference in the fight against this horrific crime."